Meanwhile, in [1]}, [2]}, it is known that the unconditional PEP with independent Rayleigh channel frequency responses \(H_i \sim \mathcal {CN} (0, 1)\)  in high SNR region is expressed as
\(&P( X \rightarrow \hat{X})\\&= \int P( X \rightarrow \hat{X}|H)p(H)dH\\&= \int Q\left(\frac{\Vert  H(X-\hat{X})\Vert }{\sqrt{2N_0}} \right)p(H)dH\\&\simeq \frac{(4N_0)^{\Gamma _{X,\hat{X}}}}{2\Pi _{i\in \mathcal {G}_{X,\hat{X}}} \eta _i }\) 
